Method and device for testing a security element of a security document

ABSTRACT

illuminating the security element (4) with at least one predetermined illumination parameter, filtering the light reflected by the security element into a first component (RLp) having a first polarisation, determining an intensity (I) of the first component (RLp) of reflected light reflected at a reflection angle (ϕR), for at least one reflection angle (ϕR), and verifying the presence of a substance (5) which has optically variable properties as a function of the intensity (I) of the first component (RLp).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is directed to a method and a device for testing asecurity element of a security document.

2. Brief Description of the Related Art

Value or security documents can contain one or a plurality of securityelements, it being possible to ascertain, for example, the authenticityof the value or security document as a function of a verification of asecurity element. In order to be able to identify, say, counterfeits ofsuch documents, it is desirable to create methods and devices for thereliable testing of such security elements.

It is known that value or security documents can contain so-calledeffect pigments. These effect pigments can configure a security element,or be part of a security element. EP 1 748 903 B1, for example,describes a machine-readable security element for security products.This publication describes optically variable platelet-shaped effectpigments which, from at least two different angles of illumination orobservation, display at least two and at most 4 optically clearlydistinguishable discrete colours. The security element can also containat least one particle-like substance with electroluminescent properties.

DE 10 2007 063 415 A1 discloses a method and a corresponding device forrecognising a product or information concerning the product. This methodidentifies a hidden coding carried by the product; the coding is givenby a set of ellipsometric parameters and the method comprises thefollowing steps:

-   -   measuring ellipsometric variables for at least one defined point        on a surface of the product,    -   comparing the measured ellipsometric variables with at least one        previously archived coding and    -   finding a match between the measured ellipsometric variables and        the archived coding or one of the archived codings, or finding a        non-match with every archived coding.

U.S. Pat. No. 6,473,165 B1 discloses an automated verification systemfor authenticating an object with an optical security feature. Theverification system comprises an optical system, a transport apparatusand an analyser. The optical system comprises one, or a plurality of,light sources for generating a narrow-band or broad-band light beam. Thetransport apparatus interacts with the light sources and is configuredin such a way that the object is positioned so that one, or a pluralityof, light beams strike a section in which the security feature is to bearranged. The analyser receives the light beams reflected by, or whichpass through, the object and is adapted so that optical properties ofthe light beams can be analysed at different angles and/or wavelengthsin order to verify the object's authenticity.

A verification can be effected as a function of the effects produced bythe optically variable effect pigments. For example, a colour shifteffect produced by the optically variable effect pigments is availablefor verification.

Nevertheless, verifying an effect produced by optically variable effectpigments, in particular the colour shift effect, can be difficult orimpossible in certain fields of application. It is also possible for theeffect produced by optically variable effect pigments such as the colourshift effect to be imitated with the help of other effect pigments. Thusthe optical verification methods which work on the basis of the producedeffect can verify one optically variable effect pigment even thoughanother effect pigment is in fact present, resulting in a falseverification.

The use of optically variable effect pigments as field displacementelements together with electroluminescent pigments is also known.Electroluminescent pigments facilitate a verification as a function ofemitted electroluminescent radiation when such an electroluminescentpigment is excited, e.g. by an electrical field. Such an excitation andverification can also be difficult or even impossible in manyapplication scenarios, such as bank ATMs. Here it can be desirable toperform a verification independently of electroluminescent radiation.

There is therefore the technical need of providing a method and a devicefor the reliable verification of a security element of a value orsecurity document which both allow reliable testing and broaden thescope within which such testing can be used.

SUMMARY OF THE INVENTION

A fundamental idea of the invention is to illuminate a security elementwith predetermined illumination parameters and to determine an intensityof a component of the light reflected by the security element which(component) is polarised with a certain polarisation, in particular atdifferent reflection angles. The presence of an effect pigment in thesecurity element, and if necessary a certain type of effect pigment, canthen be ascertained as a function of the intensity.

A method for testing a security element of a security document isproposed. The security element can be arranged or contained in, or on,the security document.

The security element can contain at least one substance with opticallyvariable properties. The substance can in particular be a particulate,preferably in power form. A particulate substance can also comprise inparticular platelet-shaped particles. The substance may also take theform of a pigment.

The security element, for example, can contain so-called fielddisplacement elements which constitute the substance which has opticallyvariable properties. Field displacement elements can be formed, forexample, from dielectric material having a dielectric constant that ischosen to be suitably high. Through the field displacement elements, anexternally imposed electrical field can be amplified in the region ofintervals left by the field displacement elements as a result of thesuitably high dielectric constant and due to the field displacementwhich this produces. This makes it possible to advantageously achieve—inthe said intervals—the field strengths needed to excite theelectroluminescence of the electroluminescent pigments; the fielddisplacement elements can be suitably dimensioned, in particular withregard to the size of the intervals left between them for the desiredamplification effect. An especially effective field compression in theintervals left by the field displacement elements can be achieved if thefield displacement elements are formed from electrically conductivematerial so that they configure so-called ‘floating’ electrodes whichare electrically isolated from their environment.

Field displacement elements can comprise a lateral size of up to approx.500 μm, in particular a size of between 2 μm and 100 μm.

To ensure a manipulation and focusing of the electrical field which isselective and can be adapted to the electroluminescent pigments whichare used, it is an advantage if the field displacement elements areapplied to a supporting body of the security document typographically,so for example with the use of a common printing method such asrotogravure or screen printing.

In addition to the electroluminescent pigments, the field displacementelements or at least some of them in the form of having a dielectricconstant of over approx. 50, preferably as electrically conductivepigments, can also be embedded in a marking layer which forms thesecurity element.

The proposed method is however also suitable for checking a securityelement which has an optically variable substance that is not configuredas a field displacement element or does not contain such fielddisplacement elements. Nor is it absolutely necessary for the securityelement to contain an electroluminescent substance such aselectroluminescent pigments.

The substance possessing optically variable properties may also bereferred to as a so-called effect pigment or may contain such effectpigments. The substance possessing optically variable properties canleave behind a different visually perceivable impression of colourand/or brightness from different illumination and/or viewing angles. Inthe case of different colour impressions this property can be referredto as ‘colour flop’. Substances in particular which comprise or producea colour flop create—in the security elements which are manufacturedwith it—non-reproducible colour and brightness impressions which can bereadily perceived by the naked eye unaided.

From at least two different illumination or viewing angles, theoptically variable substance can comprise at least two and at most fouroptically clearly distinguishable discrete colours, but preferably twosuch colours from two different illumination or viewing angles or threefrom three different illumination or viewing angles. It is preferable ifonly the discrete hues are present and no intermediate stages, i.e. aclear change can be observed from one colour to another colour when thesecurity element which contains the optically variable substance istilted. On the one hand this property makes it easier for the viewer torecognise the security element as such while making it more difficult tocopy the feature because standard commercial colour copiers cannot copyor reproduce colour flop effects.

In order to produce the full optical effect it is an advantage if theinventively deployed substance possessing the optically variableproperties is present in the security element which contains them inoriented form, i.e. it can be aligned virtually parallel to thosesurfaces of the security document which are provided with the securityelement.

Platelet-shaped effect pigments in particular can be used as anoptically variable substance. By way of example, the commerciallyavailable interference pigments marketed under the names of Iriodin®,Colorstream®, Xirallic®, Lustrepak®, Colorcrypt®, Colorcode® andSecuralic® by Merck KGaA, Mearlin® marketed by Mearl, metal effectpigments marketed by Eckhard and goniochromatic (optically variable)effect pigments such as for example Variochrom® by BASF, Chromafflair®by Flex Products Inc., Helicone® by Wacker or holographic pigmentsmarketed by Spectratec as well as other equivalent commerciallyavailable pigments can be used as platelet-shaped effect pigments. Theabove list should be regarded as being by way of example and notexhaustive.

Which hues are reflected by the optically variable substance at whichangle of incidence with white light irradiation can, in particular, beknown in advance.

Any document which is a physical entity that is protected fromunauthorised production and/or counterfeiting by security features isreferred to as a security document. Security features are features whichmake counterfeiting and/or duplicating at least difficult as comparedwith plain copying. Physical entities which contain or constitute asecurity feature may be referred to as security elements or they maycontain security elements. A security document may contain a pluralityof security features and/or security elements. In the sense of thedefinition determined here, a security document also always constitutesor contains a security element. Examples of security documents whichalso comprise value documents that represent a value include passports,identity cards, driving licences, access permits, health insurancecards, bank notes, postage stamps, bank cards, credit cards, smartcards, tickets and labels.

The proposed method comprises the method steps described below.

In a first step, the security element or a region of the securitydocument in which the security element is disposed is illuminated withat least one predetermined illumination parameter. This can be effectedwith a light source for example.

Illumination parameters include for example an illumination angle. Inthis context, the illumination angle refers to an angle of incidence ofthe light. This angle of incidence can be defined in a plane ofincidence of the light as the angle between an incident light and anormal vector of a surface of the security element or security document.A light beam of the incident light travels in the plane of incidencethat is oriented orthogonally to the previously explained surface of thesecurity element or security document.

An illumination parameter can also be a wavelength of the incidentlight. An illumination parameter can also be a polarisation state of theincident light. A polarisation state can be described for example as afunction of a polarisation azimuth and/or of a polarisation-relatedellipticity. An illumination parameter can in particular also be anintensity of the irradiated light.

It is of course conceivable for other illumination parameters of theincident light to be selected as predetermined illumination parameters.

In particular, the at least one illumination parameter can be anillumination parameter which a user can adjust.

In a second method step, the light reflected by the security element isfiltered into a first component having a first polarisation. The firstcomponent of the reflected light having a first polarisation is referredto hereinafter as the ‘first component’ for short. In particular, lightreflected by the security element or security document at apredetermined reflection angle can be filtered. Out of the lightreflected by the security element is therefore filtered a component or acomponent with a particular polarisation. A polarisation angle of thefirst component can be determined for example in relation to areflection plane or emergent plane, with the reflection plane oremergent plane being oriented at right angles to the previouslyexplained surface of the security element or security document and alight beam of the reflected light travelling in the reflection plane oremergent plane. The first component can comprise a polarisation angle of90° for example. The polarisation angle can of course also assume valuesdifferent from 90° however. This will be explained more fully below.

The filtering can be done using a means for polarisation filtering, inparticular a so-called polarisation filter.

A third method step involves determining an intensity of the firstcomponent of reflected light that is reflected at a reflection angle. Asan angle in a reflection plane of the light, the reflection angle can bedefined here as the angle between the reflected light and the normalvector of a surface of the security element or security document. Alight beam of the reflected light travels in the reflection plane thatis oriented orthogonally to the previously explained surface of thesecurity element or security document. Reflection plane can also bereferred to as emergent plane. The intensity is determined for at leastone but preferably for a plurality of different reflection angles.

A fourth method step involves verifying the presence of a substancewhich has optically variable properties as a function of the intensityof the first component. The intensity of the first component can bedetermined by a means for determining intensity, for example an opticalsensor. It may also be possible to identify a kind or type of thesubstance which has optically variable properties as a function of theintensity of the first component. The kind or type of the substance isreferred to hereinafter as ‘type’ for short. Thus a verification of thesecurity element may also be effected as a function of the identifiedtype. A type characterises a security element which consists of apredetermined material or a predetermined material composition. Theverification may also be effected depending on the reflection anglewhich can be quantitatively measured or determined for this purpose.

The proposed method makes advantageous use of two effects which areproduced by the optically variable substance. First, a polarisationstate of the irradiated light is altered by the substance which hasoptically variable properties. This means that polarisation propertiesof the light reflected by the security element differ from polarisationproperties of the irradiated light. This effect is similar to the knowneffect that at a material-specific Brewster angle, primarily one of aplurality of polarisation components of the irradiated light isreflected.

A second effect is obtained through the interference of the reflectedlight beams caused by the substance which has optically variableproperties. This interference is a function of a geometrical variable,in particular a film thickness, of the substance or of constituentparts—in particular pigments—of the substance. The interference alsodepends on orientations of the constituent parts of the substancerelative to an (idealised flat) surface of the security element orsecurity document. Thus the interference is dependent on theinhomogeneity of the surface of the security element. Since irradiatedlight can at least partly penetrate through the substance which hasoptically variable properties, the interference is also dependent onfilms, for example paper films, which lie beneath this substancerelative to the direction of irradiation. The relevant inhomogeneitiesof a surface of paper can for example be far greater than a thickness ofinterference films, and correspond for example to individual pigmentparticles or particle agglomerates.

The material composition of the security document and of the securityelement, as well as a distribution and orientation in or on the securitydocument of elements, in particular pigments, of the substance which hasoptically variable properties therefore produces a scattering of theincident light.

When they interact, both effects cause there to be a polarised lightscattering through the substance which has optically variableproperties, and the polarised light scattering in turn comprisesproperties which make it possible to verify the presence and, as isexplained more fully below, if applicable a type of the substance whichhas optically variable properties.

It is also possible that in addition to the two previously explainedeffects, scatter effects also produced for example by the inhomogeneityof the surface of the security element and films lying beneath thesecurity element, contribute to the polarised light scattering.

In particular, the aforesaid effects can cause the light that isreflected by the security element and which possesses certainpolarisation properties to display a predetermined intensity at acertain reflection angle.

The change in polarisation properties described above may be dependentin particular on the type of substance which has optically variableproperties. The change in polarisation properties may also be dependenton the at least one illumination parameter.

The presence of a substance which has optically variable properties as afunction of the intensity of the first component can for example beverified if the intensity matches a predetermined intensity or lieswithin a predetermined intensity interval. Its presence can for examplebe verified if the intensity of the first component is greater or lessthan a predetermined intensity, or lies about a predetermined intensitywithin a predetermined intensity interval.

The predetermined intensity can be ascertained for example inpreliminary tests. One type or a plurality of types of substances whichhave optically variable properties can be illuminated in preliminarytests and/or by simulation. Different test parameters can be used forthis purpose. Different illumination parameters can be selected forexample. Alternatively or cumulatively, different reflection angles canbe set. Again alternatively or cumulatively, an intensity of the firstcomponent can be determined for different polarisation states of thefirst component. A polarisation state can be described for example by apolarisation angle. Again alternatively or cumulatively, otherselectable parameters which influence the level of intensity of thefirst component can of course also be selected.

The type of substance, the set test parameters and the intensity of thefirst component recorded as a function of the set test parameters canthen be stored for example in a storage device, for example in the formof a database.

The inventively determined intensity of the first component can then becompared with stored intensities, and as a function of this comparison,the presence of at least one of a plurality of types of the substancewith optically variable properties can be verified. As well as thepresence being verified, the type can also be identified. For example,the type can be identified as a type belonging to a stored intensity if,when tested with certain test parameters, the inventively determinedintensity of the first component does not deviate, or only deviates by apredetermined amount, from the stored intensity which has been measuredunder identical test parameters. The verification of the type can besuccessful for example when the inventively identified type matches atype to be expected for the tested document. Accordingly theverification of the type cannot be successful if the inventivelyidentified type does not match the type to be expected for the testeddocument.

The proposed method advantageously facilitates a reliable verificationof at least the presence of a substance which has optically variableproperties. In particular, no excitation of electroluminescent pigmentsor an analysis of a colour shift effect is required for the verificationof the security element.

The method comprises in particular the following steps:

In one method step an intensity of the first component of the reflectedlight is determined, said light being reflected at an angle of directedreflection. The angle of directed reflection is the same in terms ofamount as the previously explained angle of incidence but it has a signthat is different in regard to a common angle convention.

In a further step an intensity of the first component of the reflectedlight is determined, said light being reflected at at least one otherreflection angle which is different from the angle of directedreflection. The at least one other reflection angle is thereforeselected to be different from the angle of directed reflection. Inparticular, in terms of value the at least one other reflection anglemay be less or greater than the angle of directed reflection. The atleast one other reflection angle can be the previously explainedreflection angle.

The intensity of the first component can as previously explained bedetermined by a means for determining intensity, for example an opticalsensor. It is possible for the first component to be filtered atdifferent angles by the same means for polarisation filtering, and itsintensity to be determined by the same means for measuring an intensity.

Alternatively it is possible for the first component when reflected atthe angle of directed reflection to be filtered by a first means forpolarisation filtering and for its intensity to be determined by a firstmeans for measuring an intensity, and for the first component whenreflected at the at least one further angle to be filtered by a furthermeans for polarisation filtering and its intensity to be determined by afurther means for measuring an intensity.

A comparison of the at least two determined intensities is carried outin a third step. A verification of the presence of a substance which hasoptically variable properties is effected if the intensity of the firstcomponent when reflected at the least one further reflection angle isgreater than the intensity of the first component when reflected at theangle of directed reflection.

It is course possible to determine the intensity of the first componentwhen reflected at a plurality of further reflection angles which are alldifferent from the angle of directed reflection.

The presence of a substance which has optically variable propertiescannot be verified if the intensity of the first component whenreflected at the angle of directed reflection is greater than theintensity/intensities of the first component when reflected at the leastone further reflection angle/the plurality of further reflection angles.

The presence of a substance which has optically variable properties canbe verified if the intensity of the first component when reflected at atleast one of these reflection angles which differ from the angle ofdirected reflection or at a plurality of such reflection angles isgreater than the intensity of the first component when reflected at theangle of directed reflection.

The proposed method advantageously facilitates a reliable verificationof at least the presence of a substance which has optically variableproperties by an easily performed comparison of at least twointensities. This comparison uses the effect that with most materials ormaterial compositions the intensity of the reflected light whenreflected at the angle of directed reflection comprises an intensitymaximum of the first component. It has been shown by experiment forexample that materials used for example in a counterfeit as a substancewhich has optically variable properties comprise an intensity maximum ofthe first component when reflected at the angle of directed reflection.

In a further embodiment the at least one reflection angle, in particularthe at least one further reflection angle, is selected as acharacteristic scattering angle, this characteristic scattering anglebeing dependent on the at least one illumination parameter and on thetype of a substance which has optically variable properties and which isto be verified.

This advantageously facilitates a reliable verification of the presenceof a substance, in particular of a predetermined type of the substance,which has optically variable properties. This in turn advantageouslyfacilitates an even more reliable verification of the security element.

In this embodiment use is made of the effect that a specific substancewhich has optically variable properties produces the previouslyexplained polarised light scattering in such a way that a maximum of theintensity of the first component occurs at the substance-specificcharacteristic scattering angle.

If therefore the presence in the security element of a certain type ofthe substance which has optically variable properties is to be verified,then the at least one further reflection angle can be selected accordingto the substance-specific characteristic scattering angle. If thespecific substance really is present in the security element then it isguaranteed with a great degree of certainty that the measured intensityof the first component when reflected at the characteristic scatteringangle is greater than the measured intensity when reflected at the angleof directed reflection. However if the intensity of the first componentmeasured at the characteristic scattering angle is less, then thepresence of the specific substance in the security element can alreadybe ruled out at this point in time.

In a preferred embodiment, a certain substance which has opticallyvariable properties is identified if the intensity of the firstcomponent when reflected at the characteristic scattering angle is atits maximum and/or matches a predetermined intensity.

In a first alternative, it is possible to determine the intensity of thefirst component when reflected at a plurality of reflection angles, forexample a plurality of reflection angles of a predetermined angleinterval, and so to determine an intensity profile over a plurality ofreflection angles. From this intensity profile it is possible todetermine a reflection angle at which the intensity of the firstcomponent is at its maximum. The type of substance which has opticallyvariable properties can then be identified as a function of thisreflection angle of maximum intensity.

For example, the type can be identified as belonging to a storedcharacteristic scattering angle if the inventively determined reflectionangle when tested with certain test parameters does not deviate or onlydeviates by a predetermined amount from this stored characteristicscattering angle which has been determined under identical testparameters. This can be carried out for example by way of a suitablyconfigured evaluation device.

To this end and as previously explained, the respectivesubstance-specific characteristic scattering angle can for example bestored in a database for different types of substances which haveoptically variable properties and if required for different testparameters as well. This information can be determined by preliminarytests for example.

Alternatively or cumulatively, the intensity of the first component ofthe light reflected at the characteristic scattering angle can becompared with predetermined intensity values. For example, thepreviously explained database can also contain alternatively orcumulatively for different types of substances, and if necessary fordifferent test parameters, intensities of the first component which aredetermined at the characteristic scattering angle. This advantageouslyfacilitates a rapid identification of a specific substance which hasoptically variable properties.

The intensity of the first component can be standardised to an intensityof the incident light for this purpose. This advantageously facilitatesa reliable determining of the intensity even with different orfluctuating intensities of the incident light.

In a method for checking a security element of a security documenttherefore, the security element can be illuminated with at least onepredetermined illumination parameter and a light reflected by thesecurity element can be filtered in a first component with a firstpolarisation. It is now possible to determine an intensity of the firstcomponent when reflected at at least the previously explainedcharacteristic scattering angle. A verification of a presence of and ifnecessary of a certain type of a specific substance which has opticallyvariable properties can be carried out if the intensity of the firstcomponent matches a predetermined intensity. This advantageouslyfacilitates a reliable intensity-based verification of a presence and anidentification of a specific substance which has optically variableproperties.

In a further embodiment, the light reflected by the security element issplit into the first component and a further component having apolarisation orthogonal to the first polarisation, with the verificationof the presence of a substance which has optically variable propertiesand/or an identification of a certain type of a substance which hasoptically variable properties being additionally effected as a functionof an intensity of that further component.

The intensity of the further component can also be determined for thispurpose. Specifically, this can be done for the light reflected at theangle of directed reflection and for the light reflected at reflectionangles that are different from that angle of directed reflection.

In this respect, a presence of a substance which has optically variableproperties can be verified as a function of a difference between theintensity of the first component and the intensity of the furthercomponent. The difference can be evaluated in the form of a differentialor a ratio, for example. For example, a presence of a substance whichhas optically variable properties can be verified if the ratio isgreater than a predetermined threshold.

This makes advantageous use of the effect that the reflected light ispolarised in a predetermined way, in particular being polarised so thata distribution of the intensity among different polarisation statescomprises a maximum and a minimum, with 90° polarisation angles lyingbetween maximum and minimum.

Alternatively or cumulatively, a certain type of a substance which hasoptically variable properties can additionally be identified as afunction of an intensity of the further component.

The intensity of the further component may be characteristic of acertain type of substance which has optically variable properties, forexample.

The difference between the intensity of the first component and theintensity of the further component, and in particular the ratio of theintensity of the first component to the intensity of the furthercomponent, can also be characteristic of a certain type of substance.

It is thus advantageous when a certain type of substance which hasoptically variable properties can be identified more reliably. Thecharacteristic intensity of the further component can also be stored inan appropriate database according to the explanations given above.

Consequently an illuminating of the security element with at least onepredetermined illumination parameter can therefore be carried out in amethod for testing a security element. The light reflected by thesecurity element can then be filtered into a first component having afirst polarisation and a further component which has a polarisationorthogonal to the first polarisation. An intensity of the firstcomponent and an intensity of the further component can then bedetermined. This can be done in particular for light which is reflectedat the previously explained characteristic scattering angle.

The presence of a substance which has optically variable properties canbe verified for example if the intensity of the first component and theintensity of the further component differ by more than a predeterminedamount, for example the presence can be verified if a ratio of theintensity of the first component to the intensity of the furthercomponent is greater than a predetermined threshold.

Alternatively or cumulatively, a certain type of the substance which hasoptically variable properties can be identified as a function of theintensity of the first and of the further component. For example boththe intensity of the first component and the intensity of the furthercomponent can be characteristic of a certain type of the substance. Thedifference between the intensity of the first component and theintensity of the further component, and in particular a ratio of theintensity of the first component to the intensity of the furthercomponent, can also be characteristic of the certain type of substance.This can be the case in particular for given test parameters, inparticular for the previously explained characteristic scattering angle.

So for example preliminary tests and/or simulations can determine whichintensities and/or which intensity ratio the first and the furthercomponent comprise when a certain type of the substance which haspredetermined test parameters is tested. As previously explained, averification can then be carried out as a function of these results.

In a further embodiment, an angle between a polarisation direction ofthe first component and a reflection plane can be selected as thecharacteristic polarisation angle, with the characteristic polarisationangle being at least dependent on the at least one illuminationparameter and on the type of a substance which has optically variableproperties and which is to be verified. Specifically, the angle betweenthe polarisation direction of the first component and the reflectionplane is selected such that an intensity of the first component comparedwith the intensities of the components with the remaining polarisationdirections is maximum. The first component is therefore filtered in sucha way that it comprises a maximum intensity on the basis of differentpolarisation directions. The corresponding polarisation angle ischaracteristic here of the type of substance which has opticallyvariable properties and is dependent on the at least one illuminationparameter.

Thus for example the angle between the polarisation direction of thefirst component and the reflection plane, and at which the firstcomponent comprises the maximum intensity, can be determined inpreliminary tests and/or simulations for different illuminationparameters and for different types of substances which have opticallyvariable properties. The said angle can be stored, e.g. in thepreviously explained database, as a characteristic polarisation angle.The angle between the polarisation direction of the first component andthe reflection plane can also be one of the previously explained testparameters.

In a subsequent test method, a means for polarisation filtering forexample can then be arranged in such a way that the reflected light isfiltered so that the polarisation direction of the first component andthe reflection plane include the characteristic polarisation angle.

Because the characteristic polarisation angle is alsosubstance-specific, the result is an advantageous increase in thereliability of the identification of a certain type of the substancewhich has optically variable properties.

In a further embodiment the security element is illuminated withlinearly polarised light. This advantageously requires a measuringdevice which is less expansive than with elliptically polarised light.

As previously explained, as well as the substance which has opticallyvariable properties the security element can contain anelectroluminescent substance, in particular electroluminescent pigments.Specifically, the substance which has optically variable properties cancontain or configure field displacement elements. In this case, andprior to the proposed method being carried out, the security element canbe applied with an electrical alternating field in order to excite theelectroluminescent pigments. An emitted luminescent light or an emittedtumescent radiation can then be measured. The inventive method can onlybe carried out here if emitted luminescent radiation is detected and/orif properties of the luminescent radiation match predeterminedproperties. Thus the inventive method can only be carried out if theelectroluminescent substance has been successfully verified.Consequently the inventive test can only be performed if a presence (ofa certain type) of an electroluminescent substance is detected. If theverification of the electroluminescent substance is not successful thenthe method can be cancelled, in which case the inventive method fortesting is not carried out.

Alternatively the inventively proposed method for testing can be carriedout first, in which case a further verification of theelectroluminescent substance is not carried out until after thesuccessful verification of the substance which has the opticallyvariable properties. For this purpose the electrical alternating fieldcan be applied to the security element to excite the electroluminescentpigments. The emitted luminescent light or the emitted luminescentradiation can then be detected. A verification of the electroluminescentsubstance can be carried out for example if emitted luminescentradiation is detected and/or if properties of the luminescent radiationmatch predetermined properties. If there is no successful verificationof the substance which has the optically variable properties, then noverification of the electroluminescent substance is carried out.

A device for testing a security element of a security document is alsoproposed; the security element can contain at least one substance whichhas optically variable properties.

The device comprises at least one light source for illuminating thesecurity element. This light source can be adjustable. Specifically,illumination parameters of the light source can be adjustable. Thus forexample a wavelength, an intensity, an angle of incidence and/or apolarisation state of the light produced by the light source can beadjusted.

It is of course conceivable that as well as the light source the devicecomprises other optical elements such as for example optical filters,modulators and means for beam guiding, it being possible to use theseoptical elements to set illumination parameters of the light produced bythe light source. Thus a polarisation state of the irradiated light canbe set by a polarisation filter for example.

The device also comprises at least one means for the polarisationfiltering of the light reflected by the security element. By way of themeans for polarisation filtering it is possible to filter a firstcomponent of the reflected light with a first polarisation filter.

For this purpose the means for polarisation filtering can be configuredand/or arranged, and in particular oriented, such that a polarisationdirection of the first component matches the previously explainedcharacteristic polarisation angle.

The device also comprises at least one first means for detecting anintensity of the first component.

The device also comprises at least one evaluation device configured forexample as a microprocessor and which can be connected for data and/orsignal transmission to the means for detecting an intensity.

An intensity of the first component of reflected light which isreflected at a reflection angle can be determined for at least onereflection angle by way of the first means for detecting an intensity.The presence of a substance which has optically variable properties as afunction of the intensity of the first component can be verified by wayof the evaluation device.

The device advantageously facilitates the performing of one of thepreviously explained methods.

In particular, an intensity of the first component of reflected lightwhich is reflected at an angle of directed reflection can be determinedby way of the first means for detecting an intensity. By way of thefirst means or of a further means for detecting an intensity it ispossible to determine an intensity of the first component of reflectedlight which is reflected at at least one further reflection angle, thisfurther reflection angle being different from the angle of directedreflection.

By way of the evaluation device it is then possible to verify thepresence of a substance which has optically variable properties if theintensity of the first component when reflected at the least one furtherreflection angle is greater than the intensity of the first componentwhen reflected at the angle of directed reflection.

The means for polarisation filtering as well as the first means fordetecting an intensity can be configured and/or arranged so that thefirst component is filtered and its intensity detected only at the angleof directed reflection.

By way of the first means for detecting an intensity it is also possibleto determine an intensity of the first component when reflected at atleast one further reflection angle which is different from the angle ofdirected reflection. For this purpose, an arrangement, in particular aposition and/or orientation, of the first means for detecting anintensity and if necessary also of the means for polarisation filteringcan be variable in such a way that only light reflected at the at leastone further reflection angle is filtered and detected. For this purposethe device can comprise a suitable adjustment apparatus for adjustingthe arrangement, in particular the position and/or orientation, of thefirst means for detecting an intensity and/or of the means forpolarisation filtering.

Alternatively, the intensity of the first component when reflected atthe at least one further reflection angle can be determined by way of afurther means for detecting an intensity. In this case the device canalso comprise a further means for polarisation filtering. The furthermeans for detecting an intensity and/or the further means forpolarisation filtering can be configured and/or arranged so that thefirst component is only filtered from light which is reflected at the atleast one further reflection angle, and its intensity determined. By wayof the evaluation device the presence of a substance which has opticallyvariable properties can be verifiable if the intensity of the firstcomponent when reflected at the least one further reflection angle isgreater than the intensity of the first component when reflected at theangle of directed reflection.

The first means for detecting an intensity and/or the at least onefurther means for detecting an intensity can be installed at a spatiallyfixed position. This means that a position and/or orientation of thecorresponding means for detecting an intensity is unchangeable.

The proposed device advantageously allows one of the previouslyexplained methods to be performed.

In a further embodiment, at least one reception angle of the first meansfor detecting an intensity can be adjusted. This means that a relativeposition and/or relative orientation of the first means for detectingthe security element can be changed. Thus for example a position and/ororientation of the first means for detecting an intensity and/or aposition and/or orientation of the security element can be changed. Inparticular, the reception angle can be selected so that a desiredreflection angle is set.

Alternatively or cumulatively the device comprises at least one furthermeans for detecting an intensity of the first component, whereby areception angle of the at least one further means for detecting anintensity can be set. This also means that a relative position and/orrelative orientation of the further means for detecting an intensity ofthe security element can be changed.

It is of course also possible to change a position and/or orientation ofthe means for polarisation filtering and/or of the further means forpolarisation filtering. A reception angle of this means for polarisationfiltering can therefore also be selected.

This advantageously facilitates the detection of intensities of thefirst component for a plurality of reception angles and hence reflectionangles. Consequently the proposed device can also be used to identifydifferent types of substances which have optically variable propertiesand which also comprise different characteristic scattering angles.

In a further embodiment, a further component having a polarisationorthogonal to the first polarisation can additionally be filtered out ofthe light reflected by the security element by way of the at least onemeans for polarisation filtering. In this case the device can comprise ameans for detecting an intensity of the further component.

The first and/or the at least one further means for polarisationfiltering may also be configured as a polarisation beam splitter or as apolarisation filter, in particular as a polarisation film.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The invention is now explained more fully by reference to a plurality ofembodiments. The figures show:

FIG. 1 a schematic representation of the method of operation of aninventive device in a first embodiment,

FIG. 2 typical profiles of intensities of a first component and secondcomponent of different types of substances which have optically variableproperties,

FIG. 3 a schematic representation of an inventive device in a secondembodiment,

FIG. 4 a schematic representation of an inventive device in a thirdembodiment,

FIG. 5 a schematic representation of an inventive device in a fourthembodiment,

FIG. 6 a schematic representation of an inventive device in a fifthembodiment,

FIG. 7 a perspective view of an inventive device and

FIG. 8 a longitudinal section through the device shown in FIG. 7 and

FIG. 9 a longitudinal section through a further inventive device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following sections the same reference signs indicate elementswith the same or similar technical features.

An inventive device 1 in a first embodiment is shown schematically inFIG. 1. Device 1 comprises a light source 2. Light source 2 radiateslight represented for example by a light beam 3, having an angle ofincidence ϕ₀ onto a security element 4 which can be part of a securitydocument (not shown). Security element 4 contains a substance 5 whichhas optically variable properties and which in particular is configuredas an effect pigment. Electroluminescent pigments 6 are arranged Inintervals between particles or elements of substance 5. Substance 5 actsas a field displacement element for field concentration in order toexcite the electroluminescence of electroluminescent pigments 6.

FIG. 1 shows that angle of incidence ϕ₀ is defined as an angle between anormal direction 7 oriented at right angles to a surface 8 of securityelement 4 or of the security document (not shown), and light beam 3.Light beam 3 shown in FIG. 1 travels in a plane of incidence (not shown)which is also oriented at right angles to surface 8 and in which aredisposed straight lines running parallel to normal direction 7. Thefigure shows that light beam 3 has a first component ELp which comprisesa polarisation plane running in the plane of incidence. Light beam 3also has a further component ELs whose polarisation plane is oriented atright angles to the plane of incidence. ELp and ELs may be any desiredorthogonal polarisation states however.

Light beam 3 comprises a predetermined wavelength and a predeterminedpolarisation state.

Device 1 also comprises a polarisation beam splitter 10, a first lightsensor 11 and a second light sensor 12. Polarisation beam splitter 10and light sensors 11,12 are disposed in such a way that light which isreflected at a predetermined reflection angle ϕ_(R) and which by way ofexample is represented by a reflected light beam 9, is filtered andreceived.

Reflection angle ϕ_(R) is defined as the angle between normal direction7 which is oriented at right angles to surface 8 of security element 4or of the security document (not shown), and reflected light beam 9,with reflected light beam 9 travelling in a reflection plane which isalso oriented at right angles to surface 8 of security element 4 or ofthe security document (not shown) and in which straight lines runningparallel to normal direction 7 are arranged.

The reflected light contains a first component RLp having a polarisationdirection which runs in the reflection plane. The reflected light alsocontains a further component RLs having a polarisation direction atright angles to the polarisation direction of first component RLp. Thefirst component RLp as well as the further component RLs are filteredout of reflected light beam 9 by polarisation beam splitter 10, with anintensity I (see FIG. 2) of the first component RLp being determined byfirst light sensor 11 and an intensity I of the further component RLsbeing determined by second light sensor 12.

Intensities I can also be determined for a plurality of reflectionangles ϕ_(R). For this purpose a position and orientation ofpolarisation beam splitter 10 and of light sensors 11,12 can be changedso that a predetermined number of different reflection angles ϕ_(R) areset. The intensities I of the first component RLp and of the furthercomponent RLs can then be determined for each of these reflection anglesϕ_(R).

For example, intensities for a predetermined number of, say, equidistantreflection angles ϕ_(R) can be detected in an angle interval of 0° to90°.

It may also be possible to determine a maximum intensity I of the firstcomponent RLp and the corresponding reflection angle ϕ_(R). Thiscorresponding reflection angle ϕ_(R) can also be referred to as thecharacteristic scattering angle ϕ₂ (see FIG. 3) which issubstance-specific. The characteristic scattering angle ϕ₂ can also bedependent on a wavelength of the irradiated light. The characteristicscattering angle ϕ₂ can also be a function of properties of securityelement 4, in particular of a surface orientation and/or roughness ofsecurity element 4. It can therefore be possible to determine thepresence and type of substance 5 or of security element 4 as a functionof the characteristic scattering angle ϕ₂.

The presence of a substance 5 can be verified for example by setting aposition and an orientation of polarisation beam splitter 10 and oflight sensors 11,12 such that the reflected light is reflected at anangle ϕ₁ (see FIG. 3) of directed reflection and its intensity I isdetected. The angle of directed reflection has the same value as theangle of incidence ϕ₀ but is oriented counter to the angle of incidenceϕ₀ in regard to normal direction 7.

The position and orientation of polarisation beam splitter 10 and oflight sensors 11,12 may also be selected such that the reflected lightis reflected at a further reflection angle ϕ_(R) which differs from theangle ϕ₁ of directed reflection. Here again, intensities I of thedifferent polarised components RLp, RLs of the reflected light can bedetected. The presence of substance 5 can be verified in this case ifintensity I of the first component RLp of the reflected light that isreflected at the angle ϕ₁ of directed reflection is less than theintensity of the first component RLp of reflected light that isreflected at the further reflection angle ϕ_(R).

It is also possible to determine a presence and if applicable a type ofsubstance 5 as a function of a difference, e.g. as a function of adifferential or ratio, of intensity I of the first component RLp andintensity I of the further component RLs at one or a plurality ofreflection angles ϕ_(R). Thus for example the difference between theintensities I of the components RLp, RLs at a predetermined reflectionangle ϕ_(R), in particular the previously explained characteristicscattering angle ϕ₂, or the curve of the difference over a plurality ofdifferent reflection angles ϕ_(R), can be characteristic of the type ofsubstance 5, i.e. substance-specific. Thus for example a certain type ofsubstance 5 can be identified if the difference between the intensitiesI of components RLp, RLs matches a difference determined for example bypreliminary tests, or a curve of the difference over a plurality ofreflection angles ϕ_(R) matches a predetermined curve or deviates fromit by only a predetermined minimal amount.

A position and orientation of polarisation beam splitter 10 and of lightsensors 11, 12, can of course be adjusted, in particular several times,until the difference, for example differential or ratio, between theintensity I of the first component RLp and of the further component RLsis maximum. The corresponding reflection angle ϕ_(R) and/or thecorresponding polarisation angle of the first component which can beadjusted by altering the orientation of polarisation beam splitter 10can be substance-specific, i.e. characteristic of a certain type ofsubstance 5. Thus the presence of and a type of a certain substance 5can be determined depending on the corresponding scattering angle ϕ_(R)and/or corresponding polarisation angle of the first component RLp.

For all of the previously explained test methods, it may be necessaryfor intensities I and/or differences between intensities I to bedetermined, e.g. in preliminary tests, for every type of substance 5 andfor different test parameters, for example illumination parameters,reflection angles ϕ_(R) and/or polarisation angles. These relationshipscan then be stored for example in a storage device, e.g. in the form ofa database. This will then facilitate the proposed verification as afunction of the stored type, test parameters and values.

FIG. 2 shows an example of an intensity profile of an intensity I of thefirst component RLp and of the further component RLs (see FIG. 1) forthree different types of substances 5 a, 5 b, 5 c for differentreflection angles ϕ_(R). It can be seen that the intensity profiles ofintensity I of the first component RLp each comprise a global maximum inan angular range of 10° to 90°. For a first substance 5 a, the maximumoccurs at a reflection angle ϕ_(R) of 60°. For a second substance 5 bthe maximum occurs at a reflection angle ϕ_(R) of 50°. With a thirdsubstance 5 c the maximum occurs at a reflection angle ϕ_(R) of 65°. Theaforesaid angles of maximum intensity I correspond to characteristicscattering angles ϕ₂ (see FIG. 3) of the different substances 5 a, 5 b,5 c and so are substance-specific.

Broken lines show intensity profiles of the further component RLs (seeFIG. 1) of the different substances 5 a, 5 b, 5 c over differentreflection angles ϕ_(R). These are roughly constant for differentreflection angles ϕ_(R) and indicate no global maximum or only one thatis difficult to identify. However it can be seen that a differencebetween the intensities I of the first components RLp and theintensities I of the further components RLs of substances 5 a, 5 b, 5 cis also maximum for the corresponding characteristic scattering angleϕ₂.

FIG. 3 is a schematic representation of a further embodiment of aproposed device 1. This is the same as device 1 shown in FIG. 1 exceptwhere stated.

As well as device 1 shown in FIG. 1, device 1 shown in FIG. 3 comprisesa polarisation filter 13 with which a desired polarisation state of theincident light beam 3 is set. The device also comprises a waveplate 14which can be configured as a λ/4 plate for example. Device 1 alsocomprises a beam splitter 15 which filters out a predetermined component17 of incident light beam 3 from incident light beam 3. Predeterminedcomponent 17 may be 5% for example. Predetermined component 17 isdetected, and its intensity determined, by a light sensor 16 which canbe configured as a photo diode for example. This makes it possible tonormalise intensities I (see FIG. 2) of the different components RLp,RLs of reflected light beams 9 a, 9 b to an intensity of incident lightbeam 3. A verification can now be carried out independently of differentintensities, and in particular independently of intensity variations ofthe incident light beam.

Incident light beam 3 comprises a predetermined wavelength, apredetermined polarisation state and a predetermined angle of incidenceϕ₀.

Device 1 also comprises a first polarisation beam splitter 10 a and afurther polarisation beam splitter 10 b. It also comprises a first lightsensor 11 a, a second light sensor 12 a, a third light sensor 11 b and afourth light sensor 12 b.

First polarisation beam splitter 10 a and first and second light sensor11 a, 12 a are arranged and configured in device 1 such that a firstreflected light beam 9 a which is reflected by security element 4 at anangle ϕ₁ of directed reflection, is filtered and the intensities of afirst component RLp and of a further component RLs of this firstreflected light beam 9 a are detected. First polarisation beam splitter10 a is configured according to polarisation beam splitter 10 shown inFIG. 1. In particular, first light sensor 11 a detects the intensity ofthe first component RLp of first reflected light beam 9 a and secondlight sensor 12 a detects the intensity I of the further component RLsof first reflected light beam 9 a.

Further polarisation beam splitter 10 b, third light sensor 11 b andfourth light sensor 12 b are arranged and configured in device 1 suchthat a further reflected light beam 9 b that is reflected at acharacteristic scattering angle ϕ₂ of a substance 5 that is to beverified (see FIG. 1), is filtered and the intensities I of the firstcomponent RLp and of the further component RLs are detected. Theintensity of the first component RLp of further reflected light beam 9 bis detected by third light sensor 11 b and intensity I of the furthercomponent RLs of the further reflected light beam 9 b is detected byfourth light sensor 12 b.

Device 1 shown in FIG. 3 is used in particular to verify a certain typeof substance 5 (see FIG. 1). Accordingly the reflection angle ϕ_(R) (seeFIG. 1) of further reflected light beam 9 b corresponds to thecharacteristic scattering angle ϕ₂ that is specific to the type ofsubstance 5 that is to be verified.

FIG. 4 shows an inventive device 1 in a further embodiment. Unlikedevice 1 shown in FIG. 3, device 1 shown in FIG. 4 comprises a firstsegmented light sensor 18 and a further segmented light sensor 19. Firstsegmented light sensor 18 comprises a first detection segment 18 a and afurther detection segment 18 b. Similarly, further segmented lightsensor 19 comprises a first detection segment 19 a and a furtherdetection segment 19 b. Different polarisation filters 20 a, 20 b, 21 a,21 b are arranged in the beam direction of reflected light beams 9 a, 9b in front of detection segments 18 a, . . . , 19 b in such a way thatfirst segment 18 a of first segmented light sensor 18 detects anintensity I of a first component RLp of a first reflected light beam 9a, with said first reflected light beam 9 a being reflected at the angleϕ₁ of directed reflection. Thus first polarisation filter 20 a filtersfirst component RLp out of first reflected light beam 9 a. Similarly,further polarisation filter 20 b filters a further component RLs out offirst reflected light beam 9 a whose intensity I is detected by furtherdetection segment 18 b of first segmented light sensor 18. A firstcomponent RLp of further reflected light beam 9 b is filtered by afurther polarisation filter 21 a, with intensity I of this firstcomponent RLp being detected by first detection segment 19 a of furthersegmented light sensor 19. Accordingly, intensity I of a furthercomponent RLs of further reflected light beam 9 b is detected by furtherdetection segment 19 b of further segmented light sensor 19, with thefurther component RLs being filtered out of further reflected light beam9 b by further polarisation filter 21 b. Here, further reflected lightbeam 9 b is reflected at a scattering angle ϕ₂ that is characteristic ofa certain type of substance 5 (see FIG. 1) of security element 4.

FIG. 5 shows an inventive device 1 in a further embodiment. Unlike theembodiments shown in FIG. 3 and FIG. 4, instead of light sensors 11 a,11 b, 12 a, 12 b, 18, 19, device 1 comprises a planar light sensor array22 which is configured as a CCD sensor and comprises a plurality oflight sensors. The figure does not shown polarisation filters which arearranged in the beam direction of reflected light beams 9 a, 9 b infront of light sensor array 22 in such a way that individual lightsensors of light sensor array 22 detect intensities 1 of differentcomponents RLp, RLs of reflected light beams 9 a, 9 b.

In this embodiment, a reflection angle ϕ_(R) of reflected light beam 9a, 9 b whose respective intensity I is being determined can bedetermined as a function of a position of the corresponding lightsensors in light sensor array 22.

In FIG. 5, light sensors (not shown) of light sensor array 22 detectintensities I of components RLp, RLs of a first reflected light beam 9 awhich is reflected by security element 4 at angle ϕ₁ of directedreflection. Similarly, further light sensors detect intensities I ofcomponents RLp, RLs of a further reflected light beam 9 b which isreflected by security element 4 at a characteristic scattering angle ϕ₂,with the characteristic scattering angle ϕ₂ being substance-specific fora certain type of a substance 5 (see FIG. 1).

A further embodiment of an inventive device 1 is shown in FIG. 6. Unlikethe embodiment of inventive device 1 shown in FIG. 4, device 1 shown inFIG. 6 comprises a third segmented light sensor 23. This segmented lightsensor 23 has a first detection segment 23 a and a further detectionsegment 23 b. Polarisation filters 24 a, 24 b are arranged in the beamdirection of a third reflected light beam 9 c in front of detectionsegments 23 a, 23 b in such a way that first detection segment 23 a candetect an intensity I of a first component RLp and further detectionsegment 23 b can detect an intensity I of a further component RLs ofthird reflected beam 9 c.

Third segmented light sensor 23 can be used to detect intensities I ofcomponents RLp, RLs of a light beam 9 c reflected at a further angle ϕ₃,as a result of which the reliability of the verification can beincreased.

FIG. 6 also shows that light source 2 irradiates onto security element 4a first light beam 3 a having a first wavelength and a second light beam3 b having a wavelength that differs from the first wavelength. Since acharacteristic scattering angle ϕ₂ can be wavelength-dependent, thereflection angle ϕ₂ shown in FIG. 6 for example can represent thesubstance-specific characteristic scattering angle in the event of anirradiation of light having the first wavelength, with the furtherreflection angle ϕ₃ representing a substance-specific characteristicscattering angle in the event of an irradiation of light having thefurther wavelength.

Thus device 1 shown in FIG. 6 facilitates the illumination of thesecurity element with two different wavelengths, making it possible todetect intensities I of components RLp, RLs of reflected light beams 9b, 9 c which when illuminated with the corresponding wavelength eachrepresent characteristic scattering angles. This advantageouslyfacilitates a further increase in the reliability of a test of securityelement 4.

Alternatively, light source 2 can irradiate onto security element 4 afirst light beam 3 a having a first polarisation and a second light beam3 b having a polarisation that differs from the first polarisation. Thisadvantageously facilitates a further increase in the reliability of atest of security element 4. Alternatively, the polarisation states ofincident light beam 3 can be modulated or altered in sequence. In thiscase the evaluation of the measured data, i.e. the evaluation ofintensities I of the components of reflected light beam/light beams 9 a,9 b, 9 c, can be synchronised with the change in the polarisation stateof incident light beam 3.

A perspective view of an inventive device 1 is shown in FIG. 7. Device 1comprises a housing 25 in which through-holes 26 a, 26 b, 26 c arearranged. Housing 25 is disposed above security element 4 and comprisesan inner volume 27 (see FIG. 8) which is open to security element 4.Through-holes 26 a, 26 b, 26 c connect inner volume 27 to outer volume28.

A light source 2 which emits light beam 3 shown for example in FIG. 1 isarranged in a first through-hole 26 a.

Polarisation filter 13, which is shown for example in FIG. 4, and awaveplate 14 are arranged in front of light source 2 looking in thedirection of irradiation. A first segmented light sensor 18 is arrangedin a second through-hole 26 b. As already described in the explanationsrelating to FIG. 4, first segmented light sensor 18 comprises a firstdetection segment 18 a and a further detection segment 18 b which areconfigured independently of one another as regards signalling.Polarisation filters 20 a, 20 b which facilitate the detection, asdescribed in relation to FIG. 4, of intensities I of differentcomponents RLp, are arranged in front of detection segments 18 a, 18 blooking in the beam direction of a first reflected light beam 9 a (seeFIG. 4).

A further segmented light sensor 19 which is configured according to theexplanations given in regard to FIG. 4 is arranged in a thirdthrough-hole 26 c.

Through-holes 26 a, 26 b, 26 c, in particular central axes of symmetryof through-holes 26 a, 26 b, 26 c, are arranged in housing 1 in such away that first segmented light sensor 18 receives a first reflectedlight beam 9 a that is reflected by security element 4 at the angle ϕ₁of directed reflection. Accordingly, further segmented light sensor 19arranged in third through-hole 26 c receives a further reflected lightbeam 9 b which is reflected by security element 4 at the characteristicscattering angle ϕ₂.

First through-hole 26 a is arranged and aligned such that light whichhas a predetermined angle of incidence ϕ₀ is irradiated onto securityelement 4.

FIG. 8 shows a longitudinal section through device 1 shown in FIG. 7. Itshows in particular inner volume 27 through which both irradiated light3 and reflected light 9 a, 9 b pass.

FIG. 9 shows a longitudinal section through a further inventive device1. It shows in particular inner volume 27 through which both irradiatedlight 3 and reflected light 9 a, 9 b pass. Unlike device 1 shown in FIG.8, a light source 2 is connected by a polarisation-maintaining lightguide 29 to a light outcoupling device 30 arranged in or on firstthrough-hole 26 a; in order to produce light beam 3, the light is guidedvia light guide 29 to light outcoupling device 30 and from there it iscoupled out to light guide 29 as light beam 3.

Light beams 9 a, 9 b reflected by through-holes 26 b, 26 c are coupledinto further polarisation-maintaining light guides 33, 34 by lightincoupling devices 31, 32, which are each arranged in or on saidthrough-holes 26 b, 26 c. The reflected light is guided by further lightguides 33, 34 to a light sensor array 22 and coupled out of furtherlight guides 33, 34 by further light outcoupling devices 35, 36. Thefigure shows that different components RLp, RLs of reflected light beams9 a, 9 b are coupled out by light outcoupling devices 35, 36 andirradiated onto light sensors (not shown) of light sensor array 22.These then detect intensities I of components RLp, RLs of reflectedlight beams 9 a, 9 b.

It is therefore possible that light for illuminating security element 4is at least partially guided via a light guide 29 from a light source 2to security element 4. Alternatively or cumulatively, light reflected bythe security element can be at least partially guided via a furtherlight guide 33, 34 from security element 4 to a light sensor.

Depicted device 1 advantageously allows light source 2 and the lightsensors to be freely positioned relative to a housing 25 or relative tosecurity element 4, thereby improving the versatility of device 1.

It is possible for polarisation beam splitting and/or polarisationfiltering to be effected by light guides 29, 33, 34 and/or lightincoupling devices 32, 33 and/or light outcoupling devices 30, 35, 36.

Light guides 29, 33, 34 can be executed as light fibres or glass fibresfor example.

LIST OF REFERENCE CHARACTERS

-   1 Device-   2 Light source-   3 Irradiated light beam-   4 Security element-   5 Substance-   5 a First substance-   5 b Second substance-   5 c Third substance-   6 Electroluminescent pigment-   7 Normal direction-   8 Surface-   9 Reflected light beam-   9 a First reflected light beam-   9 b Second reflected light beam-   9 c Third reflected light beam-   10 Polarisation beam splitter-   10 a First polarisation splitter-   10 b Other polarisation splitter-   11 First light sensor-   12 Second light sensor-   11 a First light sensor-   12 a Second light sensor-   11 b Third light sensor-   12 b Fourth light sensor-   13 Polarisation filter-   14 Waveplate-   15 Beam splitter-   16 Light sensor-   17 Component of irradiated light-   18 First segmented light sensor-   18 a First detection segment-   18 b Further detection segment-   19 Second segmented light sensor-   19 a First detection segment-   19 b Further detection segment-   20 a Polarisation filter-   20 b Polarisation filter-   21 a Polarisation filter-   21 b Polarisation filter-   22 Light sensor array-   23 Third segmented light sensor-   23 a First detection segment-   23 b Further detection segment-   24 a Polarisation filter-   24 b Polarisation filter-   25 Housing-   26 a First through-hole-   26 b Second through-hole-   26 c Third through-hole-   27 Inner volume-   28 Outer volume-   29 Light guide-   30 Light outcoupling device-   31 Light incoupling device-   32 Light incoupling device-   33 Further light guide-   34 Further light guide-   35 Further light outcoupling device-   36 Further light outcoupling device-   I intensity-   ϕ_(R) Reflection angle-   ϕ₀ Angle of incidence-   ϕ₁ Angle of directed reflection-   ϕ₂ Characteristic scattering angle-   ϕ₃ Characteristic scattering angle-   ELp First component of irradiated light-   ELs Further component of irradiated light-   RLp First component of reflected light-   RLs Further component of reflected light

The invention claimed is:
 1. A method for testing a security element (4)of a security document, the security element (4) being able to containat least one substance (5) which has optically variable properties,comprising the following method steps: illuminating the security element(4) with at least one predetermined illumination parameter, filteringthe light reflected by the security element into a first component (RLp)having a first polarisation, determining an intensity (I) of the firstcomponent (RLp) of reflected light which is reflected at a reflectionangle (ϕ_(R)), for at least one reflection angle (ϕ_(R)), whereby anintensity (I) of the first component (RLp) of reflected light which isreflected at an angle (ϕ₁) of directed reflection is determined, wherebyan intensity (I) of the first component (RLp) of reflected light whichis reflected at least one further reflection angle (ϕ_(R)) isdetermined, whereby the at least one further reflection angle (ϕ_(R))being different from the angle (ϕ₁) of directed reflection, verifyingthe presence of a substance (5) which has optically variable propertiesas a function of the intensity (I) of the first component (RLp), thepresence of the substance (5) which has optically variable propertiesbeing verified if the intensity (I) of the first component (RLp) whenreflected at the at least one further reflection angle (ϕ_(R)) isgreater than the intensity (I) of the first component (RLp) whenreflected at the angle (ϕ₁) of directed reflection.
 2. The method ofclaim 1 wherein the at least one reflection angle (ϕ_(R)) is selected asa characteristic scattering angle (ϕ₂,ϕ₃), with the characteristicscattering angle (ϕ₂,ϕ₃) being dependent on the at least oneillumination parameter and on the type of a substance (5) to be verifiedwhich has optically variable properties.
 3. The method of claim 2wherein a certain type of the substance (5) which has optically variableproperties is identified if the intensity (I) of the first component(RLp) when reflected at the characteristic scattering angle (ϕ₂,ϕ₃) ismaximum and/or matches a predetermined intensity (I).
 4. The method ofclaim 3, wherein the light reflected by the security element (4) issplit into the first component (RLp) and a further component (RLs) witha polarisation at right angles to the first polarisation, with theverification of the presence of a substance (5) which has opticallyvariable properties and/or an identification of certain type of asubstance (5) which has optically variable properties being alsoeffected as a function of an intensity (I) of the further component(RLs).
 5. The method of claim 4 wherein an angle between a polarisationdirection of the first component (RLp) and a reflection plane isselected as a characteristic polarisation angle, with the characteristicpolarisation angle being at least dependent on the at least oneillumination parameter and on the type of a substance (5) to be verifiedwhich has optically variable properties; and wherein the securityelement (4) is illuminated with linearly polarised light.
 6. The methodof claim 4, wherein an angle between a polarisation direction of thefirst component (RLp) and a reflection plane is selected as acharacteristic polarisation angle, with the characteristic polarisationangle being at least dependent on the at least one illuminationparameter and on the type of a substance (5) to be verified which hasoptically variable properties.
 7. The method of claim 3, wherein anangle between a polarisation direction of the first component (RLp) anda reflection plane is selected as a characteristic polarisation angle,with the characteristic polarisation angle being at least dependent onthe at least one illumination parameter and on the type of a substance(5) to be verified which has optically variable properties.
 8. Themethod of claim 3, wherein the security element (4) is illuminated withlinearly polarised light.
 9. The method of claim 2, wherein the lightreflected by the security element (4) is split into the first component(RLp) and a further component (RLs) with a polarisation at right anglesto the first polarisation, with the verification of the presence of asubstance (5) which has optically variable properties and/or anidentification of certain type of a substance (5) which has opticallyvariable properties being also effected as a function of an intensity(I) of the further component (RLs).
 10. The method of claim 9, whereinan angle between a polarisation direction of the first component (RLp)and a reflection plane is selected as a characteristic polarisationangle, with the characteristic polarisation angle being at leastdependent on the at least one illumination parameter and on the type ofa substance (5) to be verified which has optically variable properties.11. The method of claim 2, wherein an angle between a polarisationdirection of the first component (RLp) and a reflection plane isselected as a characteristic polarisation angle, with the characteristicpolarisation angle being at least dependent on the at least oneillumination parameter and on the type of a substance (5) to be verifiedwhich has optically variable properties.
 12. The method of claim 2,wherein the security element (4) is illuminated with linearly polarisedlight.
 13. The method of claim 1, wherein the light reflected by thesecurity element (4) is split into the first component (RLp) and afurther component (RLs) with a polarisation at right angles to the firstpolarisation, with the verification of the presence of a substance (5)which has optically variable properties and/or an identification ofcertain type of a substance (5) which has optically variable propertiesbeing also effected as a function of an intensity (I) of the furthercomponent (RLs).
 14. The method of claim 13, wherein an angle between apolarisation direction of the first component (RLp) and a reflectionplane is selected as a characteristic polarisation angle, with thecharacteristic polarisation angle being at least dependent on the atleast one illumination parameter and on the type of a substance (5) tobe verified which has optically variable properties.
 15. The method ofclaim 13 wherein the security element (4) is illuminated with linearlypolarised light.
 16. The method of claim 1, wherein an angle between apolarisation direction of the first component (RLp) and a reflectionplane is selected as a characteristic polarisation angle, with thecharacteristic polarisation angle being at least dependent on the atleast one illumination parameter and on the type of a substance (5) tobe verified which has optically variable properties.
 17. The method ofclaim 16, wherein the security element (4) is illuminated with linearlypolarised light.
 18. The method of claim 1, wherein the security element(4) is illuminated with linearly polarised light.
 19. A device fortesting a security element (4) of a security document, the securityelement (4) being able to contain at least one substance (5) which hasoptically variable properties, with the device (1) comprising at leastone light source (2) for illuminating the security element (4), whereinthe device (1) comprises at least one means for the polarisationfiltering of the light reflected by the security element (4), and by wayof the means for polarisation filtering a first component (RLp) of thereflected light can be filtered with a first polarisation, with thedevice (1) comprising at least one first means for detecting anintensity (I) of the first component (RLp), with the device (1)comprising at least one evaluation device, and by way of the first meansfor detecting an intensity (I) of the first component (RLp) of reflectedlight reflected at a reflection angle (ϕ_(R)) can be determined for atleast one reflection angle (ϕ_(R)), and by way of the first means fordetecting an intensity of the first component (RLp) of reflected lightcan be determined which is reflected at an angle (ϕ₁) of directedreflection, and by way of the first means or of a further means fordetecting an intensity (I) of the first component (RLp) of reflectedlight can be determined which is reflected at least one furtherreflection angle (ϕ_(R)), whereby the further reflection angle (ϕ_(R))being different from the angle (ϕ₁) of directed reflection, and by wayof the evaluation device a presence of a substance (5) which hasoptically variable properties can be verified as a function of theintensity (I) of the first component (RLp), with the evaluation devicebeing able to verify the presence of the substance (5) which hasoptically variable properties if the intensity (I) of the firstcomponent (RLp) when reflected at the at least one further reflectionangle (ϕ_(R)) is greater than the intensity (I) of the first component(RLp) when reflected at the angle (ϕ₁) of directed reflection.
 20. Thedevice of claim 19 wherein a reception angle of the first means fordetecting an intensity (I) is adjustable and/or the device (1) comprisesat least one further means for detecting an intensity (I) of the firstcomponent (RLp), with a reception angle of the at least one furthermeans for detecting an intensity (I) being adjustable.
 21. The device ofclaim 20 wherein a further component (RLs) can additionally be filteredout of the light reflected by the security element (4) with apolarisation at right angles to the first polarisation by way of the atleast one means for polarisation filtering.
 22. The device of claim 19wherein a further component (RLs) can additionally be filtered out ofthe light reflected by the security element (4) with a polarisation atright angles to the first polarisation by way of the at least one meansfor polarisation filtering.
 23. The method of claim 19, wherein an anglebetween a polarisation direction of the first component (RLp) and areflection plane is selected as a characteristic polarisation angle,with the characteristic polarisation angle being at least dependent onthe at least one illumination parameter and on the type of a substance(5) to be verified which has optically variable properties.